Star Trek aliens traditionally were intended to represent individual human traits, i.e., Vulcans=Logic, Ferengi=Greed, etc. I could never figure out what they were supposed to represent with all the different Xindi factions.

I always was under the impression they serve as overdrawn parallels for ethnic groups and how they were seen from a US-centric view starting with TOS. Klingons as russians, Romulans as the japanese, Cardassians as nazi germany and Ferengi as the logical conclusion of capitalist, hedonist 20th century americans.